Formation of cobalt silicides in the Co/Au/Co trilayer films on (0 0 1)Si substrate after different heat treatments has been investigated. The nucleation temperature of low-resistivity CoSi2 phase in the Co/Au/Co/(0 0 1)Si samples was found to be lowered by about 190 °C compared to what is usually needed for the growth of CoSi2. The results can be explained using the classical nucleation theory. From energy dispersive X-ray (EDAX) analysis, the Au atoms were found to diffuse from their original position to disperse in CoSi2 layer and in the grain boundaries of CoSi2 during silicidation reactions. In addition, compared with the Co/Au/(0 0 1)Si sample, the surface and interfacial roughness of CoSi2 film was effectively improved by using the Co/Au/Co sandwich structure on (0 0 1)Si.